The invention relates to switch modules suitable for making a non-blocking switch network, more particularly adapted for photonics. Nevertheless, it can also be used for making switch networks with electronic technology.
It is known that a non-blocking switch network having n.m inlets and n.m outlets, i.e. equivalent to a matrix having n.m inlets and n.m outlets can be made by using a plurality of stages each constituted by non-blocking switch matrices of size that is smaller than that of the network to be made. Such a non-blocking network is said to be a Clos network when it comprises:
a first stage constituted by c matrices, each having a inlets and b outlets;
a second stage constituted by b matrices, each having c inlets and c outlets; and
a third stage constituted by c matrices, each having b inlets and a outlets where bxe2x89xa72axe2x88x921.
By way of example, the article xe2x80x9cMultistage optoelectronic switch networksxe2x80x9d, by R. I. MacDonald et al., 8049j IEEE Proceedings-J Optoelectronics 141 (1994) June, No. 3, Part J, Stevenage Herts., GB, describes a Clos network having n.r inlets an n.r outlets and comprising three stages:
a first stage constituted by r matrices, each having n inlets and 2nxe2x88x921 outlets;
a second stage constituted by 2nxe2x88x921 matrices, each having r inlets and r outlets; and
a third stage constituted by r matrices, each having 2nxe2x88x921 inlets and n outlets.
The 2nxe2x88x921 outlets of each matrix in the first stage are connected to respective inlets of each of the 2nxe2x88x921 matrices of the second stage. The 2nxe2x88x921 inlets of each matrix in the third stage are connected to respective outlets from each of the 2nxe2x88x921 matrices of the second stage. The rxc3x97r matrices constituting the second stage are themselves three-stage Clos networks. These rxc3x97r matrices thus comprise interconnection links between a first stage and a second stage, and also between the second stage and a third stage. When the matrices are implemented using photonic technology, such links are constituted by optical fibers which cross over at very many points. The space occupied by these crossing fibers constitutes a technological limitation which makes it impossible in practice to implement optical switch networks of size greater than 128xc3x97128. Furthermore, known Clos networks cannot be under-equipped, i.e. it is not possible to avoid installing all of the matrices in the central stage even if the full capacity of a complete network is not required immediately, and this is because known networks cannot operate if any matrix in the central stage is missing.
The object of the invention is to provide a matrix capable of having greater capacity, and a switch network that can operate even if it is under-equipped.
In a first aspect, the invention provides a first type of switch module having 2p2 inlets and 2p.r outlets, wherein the inlets are grouped together in groups of p inlets and the outlets are grouped together in groups of r outlets, each group of inlets being associated with a single group of outlets; and wherein for each group of inlets the module includes means for establishing a connection between any one of the inlets of the group of inlets and any one of the outlets of the associated group of outlets.
In a second aspect, the invention provides a second type of switch module having 2p.r inlets and 2p2 outlets, wherein the inlets are grouped together in groups of r inlets and the outlets are grouped together in groups of p outlets, each group of inlets being associated with a single group of outlets; and wherein for each group of inlets the module includes means for establishing a connection between any one of the inlets of the group of inlets and any one of the outlets of the associated group of outlets.
In a third aspect, the invention provides a switch matrix having 2r.p2 inlets and 2r.p2 outlets, wherein the matrix comprises:
a first stage comprising r switch modules of the first type; and
a second stage comprising r switch modules of the second type;
and wherein the r outlets of each second switch of the switch modules of the first stage are connected to respective inlets of each of the first switches of the switch modules of the second stage in such a manner that the outlet of rank i of any second switch of rank j in the switch module of rank k in the first stage of said matrix is connected to the inlet of rank k of the switch of rank j in the switch module of rank i in the second stage of the matrix.
The matrix characterized in this way has interconnections between the r modules of the first stage and the r modules of the second stage which still cross over, but which are mutually parallel in groups of 2p links. It is thus possible to use ribbons each grouping together 2p optical fibers in parallel. The number of crossovers is thus greatly reduced. The saving in bulk occupied enables matrices of larger size to be implemented, in particular 256xc3x97256 and 512xc3x97512 matrices to be implemented.
In a fourth aspect, the invention provides a non-blocking modular switch network having n.m inlets and n.m outlets, wherein the network comprises:
a first stage having m matrices each having n inlets and 4.n.p outlets;
a second stage of 2n matrices according to claims 5 or 6; 2p outlets of each matrix of the first stage being connected to 2p respective inlets of a switch module of the first stage of each of the 2n matrices of the second stage of the network; and
a third stage of m matrices each having 4.n.p inlets and n outlets; 2p inlets of each matrix of the third switch being connected to 2p respective outlets of a switch module of the second switch of each of the 2n matrices of the second stage of the network.
The network characterized in this way presents the advantage of being capable of operating even if it is under-equipped.